Novec 7500 engineered fluid

Bare silicon wafers were obtained from University Wafers (Boston, MA). 1.5 mm and 2 mm thick poly (methyl methacrylate), PMMA, sheets were purchased from Evonik (Sanford, ME). 1 mm and 2 mm thick cyclic olefin polymer, COP, ZEONOR 1060 R sheets were purchased from Zeon Specialty Materials (San Jose, CA). Fluorinert FC 40, optiprep density gradient medium, 10-μm size streptavidin-functionalized magnetic beads, and biotin-β-Galactosidase were purchased from Sigma Aldrich (Milwaukee, WI). Novec 7500 Engineered Fluid was from 3M (Maplewood, MN). Fluorosurfactant-008 for droplet stabilization was purchased from RAN Biotechnologies (Beverly, MA). Potassium hydroxide pellets and resorufin-β-D-galactopyranoside were from Thermo Fisher Scientific (Waltham, MA). Food coloring dyes were obtained from McCormick (Baltimore, MD). Heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane used for PMMA and COP channel surface modification was purchased from Gelest (Morrisville, PA). All solutions were passed through Nylon syringe filters (0.2 μm pore size) from VWR International (Radnor, PA) to remove particulates. NdFeB permanent magnets were purchased from K&J Magnetics, Inc. (Pipersville, PA). All aqueous solutions were prepared in 18 MΩ deionized water purified using a Barnstead GenPure water purifying system from Thermo Scientific (Waltham, MA).

The following materials were used in making the PDMS-glass microfluidic devices: Sylgard 184 silicone elastomer base and curing agent (H047LAC000, Midland, MI), glass slides (1 mm thick, 12-550C, Thermo Fisher Scientific, Waltham, MA), cover glass (0.13-0.16 mm thick, 5075-1D, Thermo Fisher Scientific) and Aquapel (47112, Cranberry, PA). The SU-8 2075 photoresist used in photolithography was obtained from Kayaku Advanced Materials (Westborough, MA). The continuous phase for the water-in oil (W/O) droplets was composed of Novec 7500 engineered fluid and polytetrafluoroethylene-polyethylene glycol-polytetrafluoroethylene (PTFE-PEG-PTFE) surfactant purchased from 3M (St. Paul, MN) and Creative PEGWorks (Chapel Hill, NC), respectively. The bacteria gram staining kit, the lysogeny broth and agar media (Difco brand) were obtained from Thermo Fisher Scientific. All broth solutions and deionized water (18.3 MΩ) were autoclaved before use. The Escherichia coli (ATCC 29522) bacterial strain and resazurin sodium salt (AAB2118706) were procured from ATCC and Thermo Fisher Scientific, respectively.

Microfluidic chips were fabricated out of silicon wafers (Wafer Pro, Santa Clara, CA). Details of manufacturing microfluidic features in silicon can be found in published handbook (Rius G., et al, 2017 ). Briefly, designs were imprinted onto a 6” silicon wafer using standard photolithography techniques and features were etched using Deep Reactive Ion Etching (DRIE) in a clean room facility. Once cleaned, a borofloat glass cover slide (PG&O, Santa Ana, CA) was bonded to the silicon chip using anodic bonding. After bonding, the microfluidic channels were coated with Aquapel (Aquapel Glass, Cranberry Twp, PA) to create a hydrophobic surface. Following coating, channels were rinsed with 3 mL of Novec 7500 engineered fluid (3M, Saint Paul, MN) and then baked at 60°C for 20 min.